1. Field of the Invention
The present invention relates to a surface mount type receptacle of coaxial connector and a mounting arrangement for mounting a receptacle of a coaxial connector on a substrate, and in particular, to a surface mount type receptacle of coaxial connector and a mounting arrangement for mounting a surface mount type receptacle of a coaxial connector on a substrate which are capable of establishing a better reflection characteristic.
2. Description of the Related Art
FIG. 7 is a perspective view of a surface mount type receptacle 100e of a conventional coaxial connector, FIG. 8 is a plan view showing a structure of a bottom surface of the receptacle 100e of the conventional coaxial connector shown in FIG. 7 which opposes to a top surface of a substrate 57 shown in FIG. 9B, FIG. 9A is a front view of a plug 62 of the conventional coaxial connector shown in FIGS. 7 and 8, FIG. 9B is a cross-sectional view of the receptacle 100e of the conventional coaxial connector shown in FIG. 9A, FIG. 10A is a plan view of the substrate 57 on which the receptacle 100e of the conventional coaxial connector shown in FIGS. 9A and 9B, and FIG. 10B is a cross-sectional view of the substrate 57 along a XB-XB' line of FIG. 10A.
Referring to FIG. 10B, both of a transmission line conductor or hot-line pattern conductor 58 of a microwave transmission line such as a micro-strip line or the like and a top earth pattern conductor 59 are formed on a top surface of the substrate 57, whereas a bottom earth pattern conductor 60 is formed on all the area of the bottom surface of the substrate 57. In the specification, an electrical conductor is referred to as a conductor hereinafter.
Referring to FIGS. 7, 8 and 9B, the conventional receptacle 100e of the coaxial connector comprises:
(a) a rectangular-parallelepiped-shaped case 51 of an electrically insulating material such as a resin or the like; PA1 (b) a cylindrical inner conductor 52 arranged in the center of a cylindrical concavity 51a formed in the case 51 so that the axis direction of the inner conductor 52 is perpendicular to the bottom surface of the case 51; PA1 (c) a curved-plate-shaped or partial-cylinder-shaped outer conductor 53 formed on the inner surface of the concavity 51a; PA1 (d) a hot-line terminal 54 electrically connected to the inner conductor 52, the hot-line terminal 54 being formed so as to horizontally penetrate the case 51 from the inner conductor 52 and be taken out or extend from the inner conductor 52 through the side surface of the case 51 to the bottom surface of the case 51; and PA1 (e) an earth terminal 55 electrically connected to the outer conductor 53, the earth terminal 55 being formed so as to be taken out or extend from the outer conductor 53, horizontally penetrating the case 51 and extending through the side surface of the case to the bottom surface thereof. PA1 a case of an electrically insulating material having a top surface, side surfaces and a bottom surface to be mounted on the top surface of the substrate, said case having a concavity formed so as to extend from the top surface of said case toward the center of said case; PA1 an inner conductor arranged in said concavity of said case; PA1 an outer conductor arranged in said concavity of said case; PA1 at least one hot-line terminal formed in said case so as to be electrically connected to said inner conductor and extend from said inner conductor through the side surface of said case to the bottom surface of said case; and PA1 an earth terminal formed in said case so as to be electrically connected to said outer conductor and extend from said outer conductor to the bottom surface of said case, said earth terminal having a main portion thereof provided in said case so as to oppose to the bottom surface of said case; PA1 a case of an electrically insulating material having a top surface, side surfaces and a bottom surface to be mounted on the top surface of the substrate, said case having a concavity formed so as to extend from the top surface of said case toward the center of said case; PA1 an inner conductor arranged in said concavity of said case; PA1 an outer conductor arranged in said concavity of said case; PA1 at least one hot-line terminal formed in said case so as to be electrically connected to said inner conductor and extend from said inner conductor through the side surface of said case to the bottom surface of said case; and PA1 an earth terminal formed in said case so as to be electrically connected to said outer conductor and extend from said outer conductor to the bottom surface of said case, said earth terminal having a main portion thereof provided in said case so as to oppose to the bottom surface of said case; and
As shown in FIG. 9B, the receptacle 100e is mounted on the substrate 57 by respectively soldering the hot-line terminal 54 and the earth terminal 55 onto the hot-line pattern conductor 58 and the top earth pattern conductor 59 of the substrate 57 through solders 301 and 302. Thereafter, the plug 62 to which a coaxial cable has been attached 61 is inserted to the receptacle 100e so as to connected thereto, and then the hot-line pattern conductor 58 and the top earth pattern conductor 59 formed on the substrate 57 are electrically connected to a center conductor and an outer conductor (both not shown) of the coaxial cable 61, respectively.
In the above-mentioned conventional surface mount type receptacle 100e of the coaxial connector, the width W of the hot-line terminal 54 shown in FIG. 8 is set so that the reflection in the coaxial connector become the minimum when the substrate 57 is made of a dielectric material having a predetermined dielectric constant .epsilon..sub.r and the thickness of the substrate 57 is set to a predetermined value such as 1 mm.
In this case, when the thickness of the substrate 57 is changed or the material thereof is changed, the capacitance formed between the hot-line terminal 54 and the bottom earth pattern conductor 60 changes, and then the characteristic impedance of the coaxial connector changes. This leads to increase in the reflection, and deterioration in the electrical characteristic. In particular, recently, multi-layered substrates have been often used, and the thickness of each layer of the multi-layered substrate is small such as 0.2 to 0.3 mm. Therefore, the capacitance formed between the hot-line terminal 54 and the bottom earth pattern conductor 60 increases, and then the characteristic impedance is lowered, resulting in deterioration in the reflection characteristic.